jpa OneToMany级联操作详解之级联删除

Garage.java /** * many to one 一对多关联 */ Java代码 package com.jpa.bean1; import java.util.HashSet; import java.util.Set; import javax.persistence.CascadeType; import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.FetchType; import javax.persistence.GeneratedValue; import javax.persistence.Id; import javax.persistence.OneToMany; @Entity public class Garage { private Integer gid; private String garagenum; private Set<Auto> autos = new HashSet<Auto>(); @Id @GeneratedValue public Integer getGid() { return gid; } public void setGid(Integer gid) { this.gid = gid; } @Column(length=20) public String getGaragenum() { return garagenum; } public void setGaragenum(String garagenum) { this.garagenum = garagenum; } //CascadeType属性有四个值，其中REMOVE属性是实现级联删除，要实现级联删除 //在父栏必需添加CascadeType.REMOVE标注，这是级联删除的关键 @OneToMany(cascade={ CascadeType.REMOVE},mappedBy="garage") public Set<Auto> getAutos() { return autos; } public void setAutos(Set<Auto> autos) { this.autos = autos; } public void addGarageAuto(Auto auto) { auto.setGarage(this); this.autos.add(auto); } } Auto.java /** * one to many 多对一关联 */ Java代码 package com.jpa.bean1; import javax.persistence.CascadeType; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.Id; import javax.persistence.JoinColumn; import javax.persistence.ManyToOne; @Entity public class Auto { private Integer autoId; private String autotype; private String autonum; private Garage garage; @Id @GeneratedValue public Integer getAutoId() { return autoId; } public void setAutoId(Integer autoId) { this.autoId = autoId; } public String getAutotype() { return autotype; } public void setAutotype(String autotype) { this.autotype = autotype; } public String getAutonum() { return autonum; } public void setAutonum(String autonum) { this.autonum = autonum; } @ManyToOne() @JoinColumn(name="garageid") public Garage getGarage() { return garage; } public void setGarage(Garage garage) { this.garage = garage; } } 级联删除操作前的持久化数据 mysql> select * from garage; +-----+-----------+ | gid | garagenum | +-----+-----------+ | 1 | room1 | | 2 | room2 | | 3 | room3 | +-----+-----------+

mysql> select * from auto; +--------+---------+----------+----------+ | autoId | autonum | autotype | garageid | +--------+---------+----------+----------+ | 1 | hk2222 | car | 1 | | 2 | bj0000 | car | 1 | | 3 | jn1d31 | bus | 3 | | 4 | sh3243 | car | 3 | +--------+---------+----------+----------+ junit测试方法delete()

Java代码 @Test public void delete() { EntityManagerFactory factory = Persistence.createEntityManagerFactory("jpa-hibernate"); EntityManager em = factory.createEntityManager(); em.getTransaction().begin(); Garage garage = em.find(Garage.class, 3); em.remove(garage); em.getTransaction().commit(); em.close(); factory.close(); }

@Test public void delete() { EntityManagerFactory factory = Persistence.createEntityManagerFactory("jpa-hibernate"); EntityManager em = factory.createEntityManager(); em.getTransaction().begin(); Garage garage = em.find(Garage.class, 3); em.remove(garage); em.getTransaction().commit(); em.close(); factory.close(); } 调用delete方法是实现级联删除，此时表garage中的gid为3的字段被全部删除，同时也级联删除了与garage相关联表auto中garageid为3的字段 级联删除后的持久化数据 mysql> select * from auto; +--------+---------+----------+----------+ | autoId | autonum | autotype | garageid | +--------+---------+----------+----------+ | 1 | hk2222 | car | 1 | | 2 | bj0000 | car | 1 | +--------+---------+----------+----------+

mysql> select * from auto; +--------+---------+----------+----------+ | autoId | autonum | autotype | garageid | +--------+---------+----------+----------+ | 1 | hk2222 | car | 1 | | 2 | bj0000 | car | 1 | +--------+---------+----------+----------+